1. TAKS OBJECTIVE 3: TEKS 12 (E)
The student knows that interdependence and interactions occur within an ecosystem. The student is expected to INVESTIGATE and EXPLAIN the interactions in an ecosystem including food chains, food webs, and food pyramids.

2. Energy Flow in Ecosystems
Energy and matter flow through ecosystems.
Solar energy drives ecosystems; food webs are limited by the amount of energy that can be transferred between levels.

3. **Energy in an ecosystem originally comes from the sun
**Energy flows through Ecosystems from producers to consumers
Producers (make food)
Consumers (use food by eating producers or other consumers)
Photosynthesis
Producer
Primary Consumer
Secondary consumer
Tertiary consumer
Decomposer
Heat lost through respiration
Nutrients returned to environment

4. ARROWS SHOW FLOW OF ENERGY!!!!
Wheat
Mouse
Snake
Owl
A food chain, above, shows one path the energy can take. A food web, below, is a collection of several food chains, linked together.
ARROWS SHOW FLOW OF ENERGY!!!!
WHO EATS WHAT???
It is important for students to know arrows show where energy is flowing. From producer/ consumer to organism that is eating (receiving the energy)

5. A food (or energy) pyramid is another way to represent this information.
The pyramid gets its shape from the fact that the greatest amount of energy in the ecosystem is stored in the producers. (There is more grass than mice, and there are more mice than snakes.)
There are very few tertiary consumers in ecosystems because it takes a lot of energy feed one.

6. Toxins (poisons) can build up in the food chain
Toxins (poisons) can build up in the food chain. They are the least concentrated in the producers, but can build up in the bodies of animals as they feed. The higher an animal is on the energy pyramid, the more poison he has consumed.

7. TAKS PRACTICE

8. The diagram to the right is intended to show relationships in an ecosystem. What do the arrows represent?
A The direction of population migration
B Differences in dietary habits
C Progressively smaller organisms
D The direction of energy flow
Remember, energy flows from the producers to the primary consumers to the secondary consumers, to the tertiary consumers in webs, chains, and pyramids.

9. Which organisms in this food web can be described as both primary and secondary consumers?
F Hawks
G Weasels
H Raccoons
J Mice
Answer: *J*
Primary consumers feed off of producers (ex: plants). Secondary consumers feed off of primary consumers. Mice eat both plants (producers) and Raccoons (primary consumers) therefore, mice are considered primary and secondary consumers.

10. The diagram represents different levels of a marine food pyramid
The diagram represents different levels of a marine food pyramid. Between which two levels is the greatest amount of energy transferred?
A R and Q
B S and R
C T and S
D U and T
Remember, radiant energy from the sun is stored as chemical energy in plants. They contain the most energy in the ecosystem.

11. 4 In this food web, the bacteria probably function as —
A producers
B herbivores
C decomposers
D carnivores
Remember, bacteria can be decomposers. Also, anything that appears to be eating other dead organisms in the ecosystem is a decomposer.

12. 5. Which of these groups of organisms would most likely have accumulated the largest concentration of a long-lasting chemical pollutant in their bodies?
A Phytoplankton B Zooplankton C Lake trout
D Gulls
Remember, toxins present in small amounts on the producers, are concentrated as they pass from lower energy levels to higher ones. They become concentrated in the carnivores at the top of the food chain.

13. As matter and energy move from grasses to coyotes, the amount of available energy _____. A always decreases and population size always increases B always increases and population size always decreases C always decreases but population size may increase or decrease D increases or decreases but population size remains the same
*c*

14. Referring to Figure 3-1, the relationship between cats and mice could best be described as _____.
A predator-prey C parasite-host
B scavenger-carrion D consumer-producer
*A*
Cats eat mice; cats (predators) and mice (prey)

15. B third-order consumers C second-order consumers D decomposers
Within the above ecosystem, several interactions occur between different organisms. A food chain is illustrated in order to show a series of interactions and energy flow. Specifically, the coyotes would be considered _____.
A herbivores
B third-order consumers
C second-order consumers
D decomposers
*B* Plants are considered the producers. Therefore, the mice are 1st to consume, hence first-order consumers; Cats feed off of mice, so are second-order consumers…etc.

16. B seeds · bear · chipmunk C grass · deer · bear
Which of the following food chains correctly shows the path of matter and energy through an ecosystem?
A deer · bear · grass
B seeds · bear · chipmunk
C grass · deer · bear
D chipmunk · seeds · deer
Plants are producers and the 1st living thing to provide energy through an ecosystem. Ans: *C*

17. A The chemicals entered the air.
A manufacturing plant is located on the banks of a river. One day, toxic chemicals from the plant accidentally spilled into the river. Fish absorbed some of these chemicals into their bodies. Later, a hawk living near the river is found to have the same toxic chemicals in its system. Which statement best explains why?
A The chemicals entered the air.
B The chemicals entered the food chain.
C The chemicals were contagious.
D The chemicals are commonly found in the environment.
*B* Considering the fish from the river absorbed these chemicals, when the hawk searched for its prey, the fish, it absorbed these chemicals as well.

18. EXPLANATION

19. ECOSYSTEM: all the animals and plants found in one place, and the way they all live together
Niche-Animal’s role in the ecosystem. Types of niches:
Herbivore-eats only plants/producers,
Omnivore-eats both plants and animals,
Carnivore-eats consumers only (meat),
Predator-hunter
Prey-what is being hunted,
Decomposer-usually fungus or bacteria that eat dead material and returns nutrients to the environment (may not be included in food webs and pyramids).

20. ESSENTIAL VOCABULARY CONT’D
Producer: usually a green plant that produces its own food by photosynthesis
Consumer: primary- the organism that eats the producer
secondary- the organism that eats or derives nutrients from the first-order consumer
Biomass- the total weight of the organisms in a trophic level
Autotroph- organisms that produce their own food.
Heterotroph- organisms that eat producers; they search for their own food.
Food chain- A food chain almost always begins with a green plant (producer) which is eaten by an animal (consumer). The arrow means 'is eaten by', and shows the flow of matter and energy along the food chain. There are no decomposers in a food chain.
Food web- a network of interrelated food chains in a given area
Trophic Level- A trophic level is each level in a food chain. Matter is always 'lost' as heat energy at each trophic level.